Walter hahnemann



Dec. 22, 1925- w. HAHNEMANN METHOD OF INVESTIGATING MECHANICAL IMPULSES SUCH AS SOUND WAVES Filed July 20, 1922 Patented Dec. 22, 1925.

UNITED STATES. PATENT iOFFlCE.

WALTER HAHNEMANN, or xrrznnnne, NEAR KIEL, GERMANY, ASSIGNOR T0 SIGNAL ensnLLscHaF'r MIT nnscnnl'mx'rnn HAFTUNG, or KIEL, GERMANY, A Fri-m.

METHOD OF INVESTIGATING MECHANICAL IMPULSES SUCH AS SOUND WAVES.

Application filed July 20, 1922. Serial No. 576,310.

To all whom it may concern:

Be it known that I, WALTER HAHNEMANN, citizen of the German Republic, and residing at Kitzeberg, near Kiel, county of Schleswig-Holstein, State of Prussia, Germany, have invented certain newand useful Improvements in Methods of Investigating Mechanical Impulses Such as Sound Waves, of which the following is a specification.

This invention relates in general to methods of investigatingmechanical impulses such as sound waves and more particularly to methods of measuring short intervals of time, angles, etc. The invention is based on the following discovery:

If two impulsesreach the two earsof a person at different times the impression they make on the auditory system depends on the interval of time that elapses between the moments of their arrival at the one ear and the other car.

that when this interval is ,great two impulses that can be readily distinguished from each other are perceived one after the other,'while in cases in which the said interval is very small the impression is produced I ing upon the magnitude of the said interval.

It has hitherto been assumed that between of a single sound impulse proceeding from a certain direction, this direction dependthe region in which two distinct impulses are perceptible and the region in which only a single impulse appearing to proceed from a certain direction is perceived there is a region of uncertainty in which itis neither possible to perceive separate impulses nor to obtain a definite impression of direction. I have discovered that no such region of uncertainty exists inasmuch as in the region lying between the two afore mentioned regions the impression made on the ears of an observer is such that the soundseems to him to be coming from the extreme right or left according as the right or left ear is reached first by the arriving Hitherto it has been known sound impulses. It is on this fact that my novel method is based. I will first describe my invention as a method for finding the direction of a sound impulse. In this two sound receivers'are used which are placed a relatively great distance apart in the sound field and are each separately connected to one of the ears of the observer. This connection is established through a device that enables the moments of arrival of the sound impulses to be displaced with respect to each other and renders it possible to make their moments of arrival coincide with each other. These sound arrival displacing devices may consist either of sound conductors ofvariable lengths, or of movable vention consists in shifting the sound impulse delaying. device or variable sound conductor, or in shifting the recorded sound impressions relatively to each other, until the region is found in which the impression that the sound is coming .rom the right suddenl changes into the impression that it is coming from the left or vice versa. In other words, the zone of directionalimressions is so narrow that a very slight adustment of the compensator is required to change an extreme right impression to an extreme left impression, and vice versa.. The method of finding the direction'of sound by adjusting the sound conductors that lead to the earpieces so as to make the sound appear to be proceeding from straight ahead (the ordinary binaural method) is not employed, because the base (i. e. the distance from one sound receiver to another) is made so considerable according to the present invention that the range of angles that covers the directions of sound that could be ascertained by the method based on the physiological impression of the apparent direction would be very small, while the range of angles observable with the present method always covers 180?. On account of the great length of the base hardly any intermediate impression of soundsshifting more or less gradually from one direction to another is received at all, the direction of the sound shifting quite suddenly in the said intermediate region from the extreme right to the extreme left. or vice versa and then quickly separating again into two definite sound impulses perceived one after the other.

The receivers are spaced a relatively great distance apart, as above stated, in order to produce a 180 sound impression field in which the impression of two separated sounds occupies a relativel large portion and in which the impression of a single sound coming from a certain direction (that is, zone of directional impressions) occupies a relatively small portion. The extreme right impression may be said to form the boundary between the zone of directional impressions, and the right-hand zone of separate impulse impressions, while the extreme left impression may be said to form the boundary between the zone of directional impressions and the left-hand zone of separate impulse impressions. As the spacing between the receivers becomes increased, that is, as the base is increased, the portion of the 180 field giving separate impulse impressions lecomes enlarged, while the zone or portion of directional impressions becomes decreased, and vice versa. My invention contemplates a base of sufficient size to bring the extreme right and extreme left impressions relatively close together, because these impressions, and not the central impression as heretofore, are used in making observations or determinations.

It will appear from the above that although our novel method is more or less of a coincidence method it has nothing to do eitherwith the known interference methods or with the physiological method of determining the direction by means of a middle impression.

The novel method can, of course, be combined with the latter method. When this is done and apparatus involving, say, reproducible sound'impressions is used," it might be advantageous, in reproducing the recorded sounds, to let the recording device run slower after the apparatus has been adjusted to the point where the impression of sound coming from the/right suddenly changes to an impression of sound coming from the left.

The present invention requires, in addition to the enlarged base, a compensating arrangement having a range substantially sufficient to cover the full 180 sound impression field.

In the drawing, apparatus are diagrammatically shown which may be used for carrying out the methods hereinbefore described,

Figure l representing an aparatus forwindings of two magnets m -m arranged one above the other. These magnets are placed in close proximity to the periphery of a disk S surrounded by two steel bands or hoops s s, (Fig. 2). Two other magnets m m are also placed in close proximity to the periphery of the disk S and are arranged to be moved relatively to each other over a graduated circular scale 7:. The

windings of these magnets m m are connected to the receivers or telephones h h applied to the ears of the operator. The disk S is rotated by a motor M through the agency of a suitable intermediate gear (Fig. 2). i

The apparatus of Fig. 3 is designed on the same principle, the only difference being that styles n n n n are usedinstead of magnets m,, 11%,, m and m respectively, the stylus producing and taking off sound records on or from a grammophone plate 8,. I

When the one sound impression collecting device (m or a is moved relatively to the other (m. or 41,) two distinct impulses will at first be heard. But when the two collectors, as m and m have been set at a distance from each otherat which the sound impressions produced on the, ears almost coincide the impression of a double sound Will change into a distinct impression of. a sound proceeding from, say, the extreme right, and on the collectors being shifted further in the same direction the impression will suddenly change to that of a sound proceeding from the opposite side, and on the collector displacement being continued the single sound impression will again be resolved into a double impression. Since the base em- "ployed is a very large one it will generally be sufiicient to adjust the apparatus for the sudden change over of the impression from the right to the .left in order to be able to ascertain the magnitude to be found (direct1on or angle, time, distance), but of course 111 additlon the known psychological finding method can be made use of in the aforesaid narrow intermediate region and justed so as to obtain the impression that the sound is proceeding from straight ahead.

Fig. 4 represents the outline of a ship J at whose one side two sound receivers 61 and 6 are placed at a considerable distance apart. These receivers consist merely of air cups or the like connected by hoses Z Z to sound conductors 1' 1', of variable lengths. The other ends of these conductors are connected through hoses Z Z to earpieces 71. h,. When the tubes 0",, r, are shifted so as to cause the one to become shorter while the other grows longer the same impressions will be received by'the operator as were described in connection with the aforementioned movable sound impression reproducing arrangements.

The various Ways of carrying my novel method into effect are, of course, not limited to those illustrated herein, but may be varied in many Ways and changed by employing any other preferred known means and apparatus.

My method may be used equally well for direction finding, measuring angles, distances and times.

In direction finding the unequivocalness of the result may be established in a known manner, as for example by means of two bases extending at right angles to each other, or with the aid of a sound shadow that may be produced by the ship. The term sta tionary as used in the claims in referring to the base is intended to distinguish from a base which is revolved-or turned in making observations.

I claim 2- 1. A receiving arrangement for binaural observation of acoustic impulses, comprising two mutually unscreened receivers sepa: rately communicating with the ears of the observer, the receivers being on a stationary base of sufficient length to produce a relatively large field of separate sound impressions in the ears of the observer, and a compensating device of such range of variation that more than the full time difference of the sound impressions can be compensated when the sound arrives from an extreme lateral position.

2. A receiving arrangement for binaural observation of acoustic impulses, comprisingtwo mutually unscreened receivers separately communicatingwith the ears of the observer and spaced a sufficient distance apart on a stationary base to create a 180 impression field in which the impression of two separated sounds occupies a relatively large portion and in which the extreme right and extreme left impressions are close together,and a compensating device of suflicient range to cover the complete 180 impression field.

3. The binaural method of making observations from acoustic impulses, which comprises spacing the two receivers on a stationary base a suflicient distance apart to cause the extreme right and extreme left impressions to be positioned close together in the sound field, and utilizing these impressions for the binaural adjustment.

4. The binaural method of making observations from acoustic impulses, which comprises spacing the two receivers on a stationary base a sufficient distance apart to create a180 impression field in which the impression of two separated sounds occupies a relatively large area and in which the extreme right and extreme left impressions are close together, and utilizing these latter impressions for the binaural adjustment.

5. The binaural method of making observations from acoustic impulses, which comprises employing two mutually unscreened receivers separately communicating with the ears of the observer and on a stationary base of sufiicient length to produce a relatively large field of separate sound impressions in the ears of the observer, and bringing the sound impressions over from the zone of separated impressions into the zone of change-over from extreme right impression to extreme left impression and vice versa.

6. The binaural method of making observations from acoustic impulses, which comprises employing two mutually unscreened receivers separately communicating with the ears of the observer and on a stationary base of sufficient length to produce a relatively large field of separate sound impressions in the ears of the observer, and bringing thesound impressions over from. the zone of separated impressions into the zone of change-over from extreme right impression to extreme left impression and vice versa by making use of compensating means of sufficient range to compensate the greatest possible time intervals between the arrival of sound at the two receivers.

7. The binaural method of making observations from acoustic impulses, which comprises employing two mutually unscreened receivers separately communicating with the ears of the observer and on a stationary base of suflicient length to produce separate sound impressions in the ears of the observer, and bringing the sound impressions over from the zone of separated impressions lnto the zone of change-over from extreme right imreceivers separately communicating with the versa'by means of a traveling sound impresr ears of the observer and on a stationary base sion recorder adjustable for varying speeds 1 of suflicient length to produce separate sound in combination with a plurality of sound impressions in the ears of the observer, and impression collectors adjustablerelatively to 5 bringing the sound impressions over from each other.

the zone of separated impressions into the In testimony whereof I afiix my signature. zone of change-over from extreme right impression to extremeleft impression and vice WALTE R HAHNEMANN. 

